Liquid management member for absorbent articles

ABSTRACT

Absorbent article comprising an optional liquid permeable topsheet, an optional, sometimes liquid impermeable, backsheet, an absorbent core disposed between the topsheet and backsheet, if any, and at least one liquid management member which comprises a film having at least one microstructure-bearing hydrophilic surface that promotes rapid directional spreading of liquids, the liquid management member and core being in contact. 
     Also, liquid management members which comprise a film having at least one microstructure-bearing hydrophilic surface that promotes directional spreading of liquids. The surface has a plurality of V-shaped grooves having an angular width of Alpha, Alpha being between about 10° and about 120°. The hydrophilic surface has a contact angle with water of Theta, Theta being equal to or less than (90°−Alpha/2).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 08/293,575,filed Aug. 22, 1993, now U.S. Pat. No. 5,514,120 which is a continuationof U.S. application Ser. No. 07/986,794, filed Dec. 8, 1992, nowabandoned, which is a continuation-in-part of application Ser. No.07/809,311, filed Dec. 18, 1991 now abandoned.

FIELD OF INVENTION

The present invention relates to liquid management members for absorbentarticles such as meat tray liners, bed pads, baby diapers, sanitarynapkins, and adult incontinent pads.

BACKGROUND OF THE INVENTION

Disposable absorbent articles typically comprise three basic components:a liquid permeable topsheet that is located closest to the skin of thewearer when the article is in use, an absorbent core, and a liquidimpermeable barrier sheet which is located on the opposite side of theabsorbent core. Other components such as fastening tapes, leg and waistelastics, etc. are also commonly used.

The absorbent core receives and retains liquids that pass through theliquid permeable topsheet and typically comprises a batt of wood flufffibers. Superabsorbent materials, typically in powder form, are oftendistributed within the absorbent core to enhance its liquid holdingcapacity and liquid retention properties.

One problem associated with absorbent articles is the inefficientutilization of the total absorptive capacity of the absorbent corematerial. This is due in part because absorbent articles normally havean elongated rectangular or hourglass shape and the liquid introductionor insult and spreading of liquid is often confined to the central areaof the absorbent core.

Another problem associated with absorbent articles is the inability ofthe absorbent core to absorb liquids rapidly enough when large amountsof liquid are discharged into the absorbent core over short periods oftime. This often results in undesirable side leakage.

To improve the liquid acquisition and lateral spreading properties ofabsorbent articles, many products have utilized a wicking layer oftissue or crepe. This wicking layer can be located between the liquidpermeable topsheet and the absorbent core, in the center of theabsorbent core, or in the absorbent core in a location closer to theliquid impermeable barrier sheet. However, tissue and crepe tend topromote isotropic spreading of liquids. That is, liquid tends to spreadat similar rates in both the lengthwise and width directions of theabsorbent article. As a result, in many instances where the core iselongate, the liquid will leak beyond the side edges of the absorbentarticle before it has an opportunity to spread to the ends of theabsorbent core.

Numerous other approaches have been suggested for improving the liquiddistribution and absorption properties of absorbent articles. Most ofthese approaches have involved the use of channels, reservoirs,apertures, etc. that have been introduced into the wood fluff absorbentcore or tissue wicking layer by embossing or corrugation techniques.See, for example, U.S. Pat. No. 4,676,786 (Nishino), U.S. Pat. No.4,678,464 (Holtman), U.S. Pat. No. 4,655,759 (Romans-Hess et al.), andU.S. Pat. No. 5,030,229 (Yang).

U.S. Pat. No. 4,735,624 (Mazars) discloses a disposable diapercomprising an absorbent pad constituted by an absorbent materialconsisting essentially of hydrophilic fibers joined to one another toform a coherent mass. The pad is narrow in the crotch area and widensout in the front and rear areas of the diaper with branches.

Other approaches have been taken such as the use of nonwoven inserts asflow control zones, as disclosed in U.S. Pat. No. 4,795,453 (Wolfe) andU.S. Pat. No. 4,908,026 (Sukiennik et al.), or the use of a plasticnetting material to promote the unidirectional spreading of liquids inabsorbent pads, as disclosed in European patent 0 174 152 B1. The use ofcertain complex shaped fibers, in tow or staple form, that are capableof spontaneously transporting liquid in absorbent articles is disclosedin European patent application 0 391 814 A2 (Phillips et al.).

U.S. Pat. No. 4,798,604 (Carter) discloses a contoured polymeric filmwhich is apertured and contains a pattern of raised areas that may beemployed to form the body contacting surface, i.e, topsheet, inabsorbent devices.

Despite these previously known technologies, additional improvements toobtain more efficient and speedier absorption by absorbent cores withoutleaking are desired.

SUMMARY OF INVENTION

The present invention provides liquid management members that facilitatedesired anisotropic or directionally dependent distribution of liquids,and absorbent articles that exhibit excellent liquid acquisition anddistribution, resulting in greater effective absorption capacity andgreater comfort for the wearer.

In brief summary, articles of the invention typically comprise a liquidpermeable topsheet, a backsheet, sometimes preferably liquidimpermeable, and an absorbent core disposed between the topsheet andbacksheet, wherein the article further comprises at least one liquidmanagement member that promotes rapid directional spreading of liquids.The liquid management member is a sheet, typically flexible, having atleast one microstructure-bearing hydrophilic surface with a plurality ofchannels therein. When an absorbent article is assembled, thehydrophilic surface is in contact with the absorbent core. In someembodiments, the liquid management member is preferably impermeable,i.e., although its surface is hydrophilic the member does not transmitfluid through its body from one surface to the other surface inundesirable fashion. In some embodiments, the liquid management member(which may be impermeable or not as desired) has one or more aperturestherein to permit controlled transmission of fluid therethrough indesired manner.

In some embodiments, absorbent articles of the invention may comprise anabsorbent mass and at least one liquid management member as describedherein, and optionally an attachment member such as a layer of adhesiveor a component of a hook and loop fastening system on at least one side.

Articles of the invention may be made in the form of meat tray liners,bed pads, diapers, adult incontinent devices, and feminine hygieneproducts.

BRIEF DESCRIPTION OF DRAWING

The invention will be further explained with reference to the drawing,wherein:

FIG. 1 is a cut-away illustration of one embodiment of a diaper of theinvention;

FIG. 2 is a cross-sectional illustration of the diaper of FIG. 1;

FIGS. 3 and 4 are elevation views of illustrative embodiments of liquidmanagement members of the invention;

FIGS. 5 and 6 are cut-away illustrations of two other embodiments ofdiapers of the invention;

FIGS. 7a and 7 b are schematic diagrams used to illustrate interactionof a liquid on a surface;

FIG. 8 is a cross-sectional illustration of a portion of a film withchannels therein;

FIG. 9 is a cross-sectional illustration of a portion of a film withchannels having a different cross-sectional profile therein;

FIG. 10 is a cross-sectional illustration of a portion of a film withchannels having a different cross-sectional profile therein;

FIG. 11 is a cross-sectional illustration of a portion of a film withchannels having a different cross-sectional profile therein;

FIG. 12 is a cross-sectional illustration of another embodiment of adiaper of the invention; and

FIG. 13 is a cross-sectional illustration of another embodiment of anabsorbent article of the invention.

These figures, which are idealized, are not to scale and are intended tobe merely illustrative and non-limiting.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIGS. 1 and 2 show one embodiment of a diaper 10 of the inventioncomprising liquid management member 12. Diaper 10 also comprises liquidpermeable top sheet 14, liquid impermeable backsheet 16, and absorbentcore 18. Liquid management member 12 has at least one microstructuredhydrophilic surface 20 which promotes anisotropic, and preferably rapid,spreading of liquids in desired direction(s).

The microstructures are channels 22 in the surface of member 12.Typically they are substantially parallel and linear over at least aportion of their length. Liquid management members can be easily formedfrom thermoplastic materials by casting, profile extrusion, orembossing, preferably by casting or embossing.

Liquid management members of the invention are in the form of sheets orfilms rather than a mass of fibers. The channels of liquid managementmembers of the invention provide more effective fluid flow than isachieved with webs formed from aggregation of fibers. The walls ofchannels formed in webs of fibers will exhibit undulations and complexsurfaces that interfere with flow of liquid through the channels.

Liquid management members of the present invention are capable ofspontaneously transporting liquids along the axis of their channels. Twofactors that influence the ability of liquid management members tospontaneously transport liquids (e.g., urine and vaginal secretions)are: 1) the geometry of the surface (capillarity, shape of thechannels), and 2) the nature of the film surface (e.g., surface energy).

The channels of liquid management members of the present invention canbe of any geometry that provides desired liquid transport, andpreferably one which is readily replicated. With reference to FIG. 3,one preferred geometry is a V-groove 22. The angular width or includedangle of the V-groove (i.e., angle Alpha) can be from about 10° to about120°, preferably from about 10° to about 90°, and most preferably fromabout 20° to about 60°. It has been observed that channels with narrowerangular width provide greater vertical wicking distance. However, ifAlpha is too narrow, the wicking action will be too slow to provideliquid transport that is as fast as desired. If Alpha is too wide, thegroove may fail to provide desired wicking action. It has been observedthat as Alpha gets narrower, the contact angle of the liquid need not beas low to get similar liquid transport as the contact angle must be forgrooves with higher angular widths. The depth of the grooves (the heightof the peaks above the valleys), “d”, is typically substantiallyuniform, and is typically from about 5 to about 3000 microns, preferablyfrom about 100 to about 1500 microns, and most preferably is from about200 to about 1000 microns. It will be understood that in someembodiments members with grooves having depths larger than the indicatedranges may be used. If the grooves are too shallow, the wicking actionmay not result in fast enough movement of desired quantities of fluid.If the grooves are unduly deep, the overall thickness of the liquidmanagement member will be unnecessarily high and the member may tend tobe stiffer than is desired.

When used in absorbent articles it is typically preferred that theliquid management members be thin and flexible to avoid impartingundesirable stiffness to the absorbent articles. For instance, in thecase of liquid management members used in infant diapers or adultincontinent devices, the thickness typically ranges from about 10 toabout 1500 microns, preferably from about 125 to about 1000 microns. Theliquid management member should be sufficiently thick to retain itsstructural integrity when subjected to stresses (e.g., stretching andflexing) expected to be encountered during use. In the case of bed pads,the absorbent article need not be as highly flexible to provide comfortand the liquid management member may be up to 3000 microns or morethick.

Liquid management members can be formed from any thermoplastic materialssuitable for casting, profile extrusion, or embossing including, forexample, polyolefins, polyesters, polyamides, poly(vinyl chloride), etc.Polyolefins are preferred, particularly polyethylene or polypropylene,blends and/or copolymers thereof, and copolymers of propylene and/orethylene with minor proportions of other monomers, such asethylene/vinyl acetate. Polyolefins are preferred because of theirexcellent physical properties, ease of processing, and typically lowercost than other thermoplastic materials having similar characteristics.Polyolefins readily replicate the surface of a casting or embossing rolland are also readily profile extruded. They are tough, durable and holdtheir shape well, thus making such films easy to handle after thecasting or embossing process. A particularly preferred polyolefin foruse in the present invention is TENITE™ 1550P Polyethylene, a lowdensity polyethylene from Eastman Chemical Company, having a melt flowindex of 3.5 grams/10 minutes (ASTM D1238) at 190° C. and a density of0.918 (ASTM D1505). Alternatively, liquid management members can be castfrom curable resin materials such as acrylates or epoxies, and cured byexposure to heat or UV or E-beam radiation. Preferably, the liquidmanagement member substantially retains its geometry and surfacecharacteristics upon exposure to liquids.

Generally, the susceptibility of a solid surface to be wet out by aliquid is characterized by the contact angle that the liquid makes withthe solid surface after being deposited on the horizontally disposedsurface and allowed to stabilize thereon. It is sometimes referred to asthe “static equilibrium contact angle”, sometimes referred to hereinmerely as “contact angle”. As shown in FIGS. 7a and 7 b, the contactangle Theta is the angle between a line tangent to the surface of a beadof liquid on a surface at its point of contact to the surface and theplane of the surface. A bead of liquid whose tangent was perpendicularto the plane of the surface would have a contact angle of 90°.Typically, if the contact angle is 90° or less, as shown in FIG. 7a, thesolid surface is considered to be wet by the liquid. Surfaces on whichdrops of water or aqueous solutions exhibit a contact angle of less than90° are commonly referred to as “hydrophilic”. As used herein,“hydrophilic” is used only to refer to the surface characteristics of amaterial, i.e., that it is wet by aqueous solutions, and does notexpress whether or not the material absorbs aqueous solutions.Accordingly, a material may be referred to as hydrophilic whether or nota sheet of the material is impermeable or permeable to aqueoussolutions. Thus, hydrophilic films used in liquid management members ofthe invention may be formed from films prepared from resin materialsthat are inherently hydrophilic, such as for example, poly(vinylalcohol). Liquids which yield a contact angle of near zero on a surfaceare considered to completely wet out the surface. Polyolefins, however,are typically inherently hydrophobic, and the contact angle of apolyolefin film, such as polyethylene or polypropylene, with water istypically greater than 90°, such as shown in FIG. 7b. Body liquids thatwill come into contact with the liquid management members of the presentinvention are aqueous. Thus, if such films are used as liquid managementmembers of the invention, they must be modified, e.g., by surfacetreatment, application of surface coatings, or incorporation of selectedagents, such that the surface is rendered hydrophilic so as to exhibit acontact angle of 90° or less, thereby enhancing the wetting and liquidtransport properties of the liquid management member.

In liquid management members of the invention having V-grooves, thedesired surface energy of the microstructured surface of the liquidmanagement member is such that

Theta≦(90°−Alpha/2),

wherein Theta is the contact angle of the liquid with the member andAlpha is the angular width of the groove.

Any suitable known method may be utilized to achieve a hydrophilicsurface on liquid management members of the present invention. Surfacetreatments may be employed such as topical application of a surfactant,plasma treatment, grafting hydrophilic moieties onto the film surface,sol-gel coating, corona or flame treatment, etc. Alternatively, asurfactant or other suitable agent may be blended with the resin as aninternal additive at the time of film extrusion. It is typicallypreferred to incorporate a surfactant in the polymeric composition fromwhich the liquid management member is made rather than rely upon topicalapplication of a surfactant coating. Topically applied coatings tend tofill in, i.e., blunt, the notches of the channels, thereby interferingwith the desired liquid flow to which the invention is directed. Anillustrative example of a surfactant that can be incorporated inpolyethylene liquid management members is TRITON™ X-100, anoctylphenoxypolyethoxyethanol nonionic surfactant, e.g., used at betweenabout 0.1 and 0.5 weight percent. An illustrative method for surfacemodification of the members of the present invention is the topicalapplication of a 1 percent aqueous solution of the reaction productcomprising 90 weight percent or more of:

wherein n=8 (97 percent), n=7 (3 percent), and 10 weight percent or lessof:

wherein n=8 (97 percent), n=7 (3 percent). Preparation of such agents isdisclosed in U.S. Pat. No. 2,915,554 (Ahlbrecht et al.)

In some embodiments, liquid management member 12 will have channels ononly one major surface as shown in FIG. 2. In other embodiments,however, liquid management member 12 will have channels on both majorsurfaces, as shown in FIGS. 3 and 4. Typically in the case of absorbentarticles such as diapers, if the member has channels on both majorsurfaces, the channels on one surface are substantially parallel tothose on the other surface. The channels may be laterally offset fromone surface to the other surface as shown in FIG. 3 or may be aligneddirectly opposite each other as shown in FIG. 4. A liquid managementmember with offset channels as shown in FIG. 3 provides a maximum amountof surface area for wicking while at the same time using a minimumamount of material. In addition, a liquid management member with offsetchannels can be made so as to feel softer due to the reduced thicknessand boardiness of the sheet than a liquid management member with alignedchannels as shown in FIG. 4. As shown in FIG. 4, liquid managementmembers 12 of the invention may have one or more apertures 24 thereinwhich enable a portion of the liquid in contact with the front surfaceof the liquid management member to be transported to the back surface ofthe member to improve the control thereof in accordance with theinvention. The apertures need not be aligned with the notch of a channeland do not need to be of about equal width as the channels. The surfacesof the liquid management member within the apertures is preferablyhydrophilic.

Liquid management member 12 can be incorporated into disposableabsorbent article 10 in a number of ways. The member can be cut into oneor more generally longitudinal strips that can be placed above, below,or within the absorbent core in a variety of configurations. Severalillustrative embodiments are depicted in FIGS. 1, 5, and 6. Diaper 510in FIG. 5 has three liquid management members 512 with channels 521arranged in parallel strips in absorbent core 518. Diaper 610 in FIG. 6has two liquid management members 612 overlaid in an intersecting or “X”pattern in absorbent core 618. Typically, the intersection will belocated where liquid introduction is expected.

If desired, the liquid management member may be disposed on the interiorsurface of the backsheet or even made integral therewith by forming thedesired microstructured surface on the interior surface thereof. In thisembodiment, the microstructured film serves two functions, as a liquidtransport layer adjacent to the underside of the absorbent core and as aliquid barrier layer for the absorbent article. FIG. 12 illustratesdiaper 120 of the invention comprising liquid permeable topsheet 1214,liquid impermeable backsheet 1216, and absorbent core 1218. Liquidmanagement member 1212, with microstructured surface 1220 with grooves1222, is disposed on the interior surface of backsheet 1216. If desired,grooves 1222 may be formed on the surface of backsheet 1216 such thatthe liquid management member and backsheet are of unitary construction.

As mentioned above, a preferred microstructure is one in which thechannels are V-shaped grooves, i.e., each channel is defined by a pairof planar walls which meet at a line of intersection. Such channels areeasily formed and provide rapid liquid transport. In other embodiments,the sides of the channel need not be planar but the channel preferablypossesses a notch that extends parallel to the longitudinal axis of thechannel. In other words, when viewed in cross-section, the line ofintersection of a plane perpendicular to the axis of the channel and thewalls of the channel preferably passes an abrupt slope change, i.e., ageometric discontinuity or a point where the first order derivative ofthe surface of the channel has multiple values. Although preferred, thenotch need not be a perfect V point; typically, useful liquid managementis achieved if the notch has a radius of curvature of about 25 micronsor less, preferably about 10 microns or less, and more preferably about5 microns or less. It has been observed that coatings applied tomicrostructured surfaces to impart desired hydrophilicity thereto maytend to aggregate or pool in the base of the channel, tending toincrease the radius of notch. FIG. 8 shows a typical member withV-shaped grooves 22 having notch or abrupt slope change 23, FIG. 9 showsa member with channels 921 having non-planar, inwardly flaring walls anda base with abrupt slope change 923, and FIG. 10 shows a member withchannels 1021 having non-planar walls and no abrupt slope change. Theliquid management member in FIG. 9 has large crests 924 between adjacentchannels 921. It is typically preferred to have narrow crests or, asshown in FIG. 8, closely packed channels such that the walls of adjacentchannels are in contact in order to increase the number of channels perunit surface width. FIG. 11 shows a preferred embodiment of liquidmanagement member 1110 of the invention wherein channels 1121 have notchor abrupt slope change 1123 and walls 1124 flare outwardly rather thanbeing straight. For ease of manufacture, the walls between adjacentchannels preferably meet at crests 1126 with minimum land area, i.e., ahigh channel density.

Preferably the channel walls are smooth because an excessive amount ofsurface roughness will tend to impede desired liquid flow. Liquidmanagement members with channel walls that flare outwardly as shown inFIG. 11 are believed to provide an optimum combination of rapidanisotropic fluid flow and vertical wicking capability and accordinglyare preferred for many applications.

Typically, the channels in liquid management members of the inventionare oriented in the same direction, i.e., they are substantiallyparallel throughout their entire length. Channels are considered to besubstantially parallel as long as they extend in the same generaldirection without intersecting; their lateral spacing need not be equalover their entire length.

In a typical absorbent article of the invention as shown in FIG. 1,absorbent core 18 and liquid management member 12 are both elongate andoriented in the same general direction. It is typically preferred thatthe liquid management member be substantially coextensive with theabsorbent core i.e., extend to within about 1 to 2 centimeters of theedge of the absorbent core in most cases. It is also typically preferredthat it not extend beyond the absorbent core as this may result inleaking. In such instances, the channels of the liquid management memberwill typically be oriented along the longitudinal axis of the member andof the absorbent core. Referring again to FIG. 1, it will typically bepreferred in such instances for the lateral spacing of channels 22 tovary along their longitudinal axis with the spacing being at a minimumin a longitudinally interior region of member 12 and being wider thanthe minimum at an exterior region of member 12. Such an article istypically constructed such that the region of minimum lateral spacing islocated near expected liquid insult with the wider spacing being locatedat more distant locations. In such embodiments, liquid management member12 provides both improved transport of the liquid away from the insultbut also improved distribution of the liquid to more distant portions ofabsorbent core 18. If desired, additional channels (not shown) may beginbetween the interior region and longitudinal edges of liquid managementmember 12.

FIG. 13 shows another embodiment of the invention with absorbent article1300 comprising liquid management member 1302 withmicrostructure-bearing surface 1304, absorbent mass 1306, and attachmentmember 1308 on at least one side. Attachment member 1308 is selected inpart based on the substrate to which the absorbent article is to beattached. Illustrative examples include suitable adhesives. Otherillustrative examples include a component of a hook and loop fasteningsystem, i.e., a strip of hook material with the strip of loop materialbeing applied to a substrate.

Usually the microstructured surface is in contact with the absorbentcore. However, in some embodiments, for instance where the absorbentmaterial is subject to gel blocking, the liquid management member willbe oriented such that a microstructure-bearing surface and the absorbentcore are disposed on opposite sides of the liquid management member. Insuch embodiments, the liquid management member is preferably smallerthan the absorbent core and/or has apertures therein. In someembodiments, the liquid management member may comprise anothermicrostructure-bearing surface as described herein on the same side asthe absorbent core.

Absorbent articles of the invention may be used in a variety ofapplications. For instance, meat tray liners may be made with liquidmanagement members as described herein. In such embodiments the packageis assembled with the topsheet in contact with the meat. The backsheetmay be permeable or impermeable.

In simple embodiments, absorbent articles may consist essentially of anabsorbent core and liquid management member of the invention.

EXAMPLES

The invention will be further explained by the following illustrativeexamples which are intended to be nonlimiting.

Unless otherwise indicated, the liquid management members used in thefollowing examples were made from sheets of low density polyethylene,TENITE™ 1550P from Eastman Chemical Company.

Each liquid management member was formed by stamping the sheet with amicrostructured nickel tool to form microstructured channels inaccordance with invention. The nickel tools were produced by shaping asmooth acrylic surface with diamond scoring tools to produce the desiredstructure and then electroplating the structure to form a nickel toolwith the indicated structure. Unless otherwise indicated, the tools usedeach provided a group 3.8 centimeters (1.5 inches) wide of a pluralityof evenly spaced parallel channels. The tools each had a structuredsurface with channel forming elements as follows: ribs corresponding inprofile to the resultant channels, the crests or tips of the ribscorresponding to the bases or notches in the resultant channels, thecreases between adjacent ribs corresponding to the land area betweenadjacent channels. Unless otherwise indicated, the master tools used hadthe following features:

Tool Features Format Spacing¹ Depth² Tip³ Angle⁴ 1 0.240 0.33 NA 40 ° 20.520 0.33 NA 10 °/70 ° 3 0.496 0.33 NA 20 °/60 ° 4 0.330 0.46 2.5 40 °5 0.362 0.46 25 40 ° ¹Spacing is the distance between adjacent tips ofthe tool in millimeters. ²Depth is the vertical depth of the channels inmillimeters. ³Radius of curvature of the tip which forms the notch inthe liquid management member in microns. ⁴Angle is the included angle ofthe ribs in degrees.

In formats 1, 2, and 3 the tips of each rib were defined by theintersection of two planes formed by a diamond scoring tool and theradius is indicated as NA. In formats 4 and 5 the tips were shaped witha diamond scoring tool to have the indicated radius of curvature.

In each of formats 1, 4, and 5 the ribs were of uniform profile. Informat 2 ribs having a 10° included angle alternated with ribs having a70° included angle. In format 3 ribs having a 20° included anglealternated with ribs having a 60° included angle.

The liquid management members formed from each tool are indicated belowby identifying the format number from the table above. In someinstances, the tool described above was used to from a mirror image toolvia electroplating. The mirror image tool was then used to form a liquidmanagement member. In those instances, the liquid management member isindicated by identifying the format number from the table above with aprime “′” notation. For example, a liquid management member formed withtool format 1 will be identified with format number “1” whereas a liquidmanagement member formed with a mirror image tool which was formed fromtool format 1 will be identified with format number “1′”.

Example 1

Liquid management members were formed according to the method describedusing other nickel tools to yield V-shaped grooves having the indicatedangular width and depth. 0.4 weight percent of polymer grade zincstearate was included in the polyethylene as a slip agent.

Vertical wicking was measured in accordance with DIN 53924 (“DeutschesInstitut Fuer Normung”). The vertical height achieved in 3 minutes bysynthetic urine is reported. Horizontal wicking was evaluated bymeasuring the maximum spread achieved by a 0.037 gram sample ofsynthetic urine. A liquid comprising:

Amount (grams) Component 0.6 calcium chloride  1.00 magnesium sulfate 3.30 sodium chloride 19.40 urea

in sufficient deionized water to yield 1000 milliliters was used assynthetic urine. This liquid has been determined, using the WilhelmyBalance Technique, to have a surface tension of about 61 to about 63dynes/centimeter. A sufficient amount of blue colorant, K7117 D+C BlueNo. 1, from H. Kohnstamm and Company, Inc. was added to render thesolution dark blue to facilitate observations during testing.

Liquid management members were formed with adjacent (i.e., substantiallyno land area between neighboring grooves) V-shaped grooves having theindicated angular width and depth. A coating of a solution in deionizedwater of 1 weight percent of:

wherein n=8 (97 percent), n=7 (3 percent), and 10 weight percent or lessof:

wherein n=8 (97 percent), n=7 (3 percent), was applied to provide acoating thickness (wet) of about 25 microns, and the members were thenoven dried at 93° C. (200° F.) for 15 minutes.

The following liquid management results were obtained:

Groove Wicking Alpha Depth¹ H² V³ 120 ° 100 11.5 0.7  90 ° 175 15.7 1.1 70 ° 175 15.7 2.2  60 ° 175 17.1 4.0  40 ° 225 16.8 6.1 ¹In microns.²Horizontal Wicking in centimeters. ³Vertical Wicking in centimeters.

Example 2

To assess the relationship of notch sharpness on vertical wicking liquidmanagement members formed from tools 1′, 4, and 5 were tested forvertical wicking as in Example 1 except the fluid used was deionizedwater containing 0.1 weight percent of fluorescent dye,2-(6-hydroxy-3-oxo-3H-xanthen-9-yl) benzoic acid disodium salt, afluorescein disodium salt from Eastman Kodak Company. This liquid hasbeen determined, using the Wilhelmy Balance Technique, to have a surfacetension of about 74 to 75 dynes/centimeter. The following results wereobtained:

Sample Format Radius¹ Vertical Wicking² 2-1 1′ 1.1 10.40 2-2 4 2.3  9.152-2 5 26.  5.65 ¹Average measured radius of curvature of channel notchin microns. ²Vertical height achieved in centimeters.

The notch radius of curvature of the liquid management members wereobtained by taking a photomicrograph of the channel cross section with ascanning electron microscope. The polymeric liquid management memberswere potted in an epoxy which was allowed to cure and then the samplewas ground down and polished leaving an exposed cross section of thechannel. A photomicrograph of this prepared sample was then taken.Tangent lines were drawn along several points of the tip of the channel.Normal lines to where the tangents contacted the channel were drawn andthe location of their intersection identified as the center of curvatureof the channel. An average arc radius was then fit to the tip curvature,with the center being the intersection of the normal lines. The arcradius length was then recorded as the radius of curvature reportedabove.

Example 3

To assess the effects that angular width (Alpha) of the channels andsurface properties of the liquid management member (affected by usingsurfactant) have on vertical wicking distance, vertical wicking testswere performed as in Example 2 using the indicated liquid managementmembers. The vertical wicking results in centimeters were as follows:

Surfactant (see below) Sample Alpha A B C D 3-1 120  2.1 3.3 6.1 1.8 3-290 2.0 3.4 6.3 2.5 3-3 70 2.5 5.0 7.5 4.8 3-4 60 2.7 7.5 8.1 4.9 3-5 404.1 9.5 11.5  9.6 3-6 20 8.6 11.6  11.9  11.5  3-7 10 9.1 13.5  14.2 13.7  A A surfactant solution was topically applied as in Example 1. B0.1 weight percent of the surfactant solution used in Example 1 wasincluded in the polymer melt. C 0.5 weight percent of TRITON ™ X-100 wasincluded in the polymer melt. D 0.5 weight percent of PS071,dimethylsiloxanealkylene oxide copolymer from Patriarch Chemical, wasincluded in the polymer melt.

Tool format 3 was used to make the liquid management member in Sample3-6. Tool format 2 was used to make the liquid management member inSample 3-7. The vertical wicking results reported were measured from thechannels with the narrow angular width in each Sample.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention.

What is claimed is:
 1. A liquid management member which comprises a film of impermeable material having at least one microstructure-bearing hydrophilic surface that promotes directional spreading of liquids, said surface having a plurality of V-shaped grooves therein, wherein said grooves are spaced apart laterally and the angular width of said grooves is Alpha, said Alpha being between about 10° and about 120°, and said hydrophilic surface has a contact angle with water of Theta, said Theta being equal to or less than (90°−Alpha/2).
 2. The article of claim 1 wherein the angular width of said grooves is between about 10° and about 90°.
 3. The article of claim 1 wherein the angular width of said grooves is between about 20° and about 60°.
 4. The article of claim 1 wherein said grooves are between about 5 and about 3000 microns deep.
 5. The article of claim 1 wherein said grooves are between about 100 and about 1500 microns deep.
 6. The article of claim 1 wherein said grooves are between about 200 and about 1000 microns deep.
 7. The article of claim 1 wherein said liquid management member is impermeable to aqueous liquids.
 8. The article of claim 1 wherein said liquid management member has a thickness of between about 125 and 1000 microns.
 9. The article of claim 1 wherein said liquid management member has one or more apertures therein.
 10. The article of claim 1 wherein said liquid management member is made of one or more polyolefins.
 11. The article of claim 1 wherein said grooves are substantially parallel throughout their length.
 12. The article of claim 1 wherein said liquid management member is elongate, said grooves are oriented along the longitudinal axis of said liquid management member.
 13. The article of claim 1 wherein the lateral spacing of said grooves varies along their longitudinal axis.
 14. The article of claim 13 wherein the lateral spacing of said grooves is at a minimum in a longitudinally interior region of said grooves and wherein the lateral spacing of said grooves is wider than said minimum at an exterior region of said grooves.
 15. The article of claim 1 wherein said film is flexible. 